Dilmunia Rock (Bahrain)

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Part of the regional summary: Bahrain

Photo: Anderson Mayfield/Coral Reef Diagnostics

Country

Bahrain

Survey date(s)

2023-09-23

Coordinates

26.2850, 50.6350

This site is in the vicinity of a land-based point.

Coral cover

0.5%^*

Claude computer vision (10 edited photos) · other methods below · median 0.0%

*Based on only 10 reef-habitat photos; this estimate is less certain.

Observations

None tagged; see Stressors below

Heat stress

Most recent heat load record

32.6°C 11.1°C-weeks

26 Oct 2026 · NOAA alert that day: no stress (water now below the bleaching threshold; 11.1°C-weeks built up over the last 12 weeks)

5-year thermal stress load

5-year mean max. degree heating weeks (DHW)

9.9°C-weeksⁱ

2021–2025

NOAA Coral Reef Watch — Bahrain virtual station

i 5-year mean max. DHW is the mean of the annual maximum DHWs over the five complete years named above, not conditions today.

More info

Bahrain (NOAA CRW virtual station)

Photographs

15 shown on this page

Site summary

Read this summary in:

Dilmunia Rock is a shallow site less than 2 km off Bahrain; published site descriptions give it a rocky ledge near 5 m dropping to sand and say it is known locally for its fish life. Anderson's photographs show turf-covered rock with little coral, plus snapper-like fish, jacks, sea urchins, and a drifting jellyfish.

Max. depth dived

9 m

dive-log maximum

Water temp. during survey

34.0°Cⁱⁱ

+6.9°C vs the 2023 mean sea temperature (27.1°C)

ii Single water temperature in Anderson's DiverLog record for this dive (the dive computer stored one value, probably a dive mean).

More info

Note: NOAA's regional station series averages 1.1°C warmer than the satellite pixel nearest this site (1.5 km away), which is used here instead.

Bottom time

45 min

in at 15:15

One other CRD dive site with its own page within 5 km shown in orange — click a marker to open its page.

Site description

Setting

Dilmunia Rock is a shallow site less than 2 km off Bahrain in the Arabian Gulf (26.285 N, 50.635 E). Published site descriptions — not observations of Anderson's — place it between roughly 5 and 10 m, with a rocky ledge near 5 m giving way to a sand bottom below (e.g., Image 4, Image 6, Image 10, Image 11, Image 12).

The same published descriptions say it is known locally for its fish life and suitable for both beginner and experienced divers.

General benthic features

Anderson's photographs show low rock ledges and boulders carpeted in reddish-brown and green algal turf, with patches of sand between them (e.g., Image 6, Image 7, Image 10, Image 11, Image 12, Image 14); coral is scarce in the frames.

Coral cover

Reference: Claude CV point count (this site's photos)
Coral cover: 0.5% — a blind Claude computer-vision point count of 10 of Anderson's edited photographs (20 points per photo; water, fish, and obstructions excluded). Other computer-vision methods are listed in the method table. There is no personal or nearby independent survey data for the site.

Stressors

As regional context rather than an account of this reef: Gulf water ranges seasonally between about 16 and 36°C, and Bahrain's reefs lost most of their coral in mass bleaching events in 1996 and 1998 and bleached severely again in 2017 (AlMealla et al. 2024, Marine Biology 171:39, doi:10.1007/s00227-023-04351-9). The satellite-derived five-year mean annual maximum heat stress at NOAA Coral Reef Watch's Bahrain virtual station is 9.9 degree heating weeks. No crown-of-thorns starfish (COTS) or other corallivores were evident.

Fish and other fauna

Yellow-striped fish that appear to be snappers shelter under a ledge (e.g., Image 5), a group of silvery, jack-like fish passes over the sand (e.g., Image 9), and schools of small baitfish fill the open water (e.g., Image 13, Image 18).

Long-spined sea urchins sit on the rock (e.g., Image 8, Image 17), and a long-tentacled jellyfish drifts in the water column (e.g., Image 15, Image 16).

Comparisons with other data

We found no other surveys at this site as of 2026. If you would like to share yours, please email us.

Dive record

We dived it on 23 September 2023.

Other notes

The photographs from that dive are published here.

CV model comparison

Mean 0.5%, median 0.0% across 10 photos.

More info

A few colony-focused photos raise the mean; the median is the typical photo. No computer-vision method yet estimates coral cover accurately on new images, so treat this as indicative rather than a measurement; it is revised as the methods improve.

Headline: Claude computer vision — a blind point count of this site's own photographs.

More info

CoralSCOP was run on the same photos and is listed for comparison. No diver transect exists for this trip, so agreement between the rows is not accuracy, and no computer-vision method yet estimates coral cover accurately on new images; treat every row as indicative.

Method	Hard coral cover (%)	Photos (n) ± SE
CoralSCOP edited	5.0*	n = 10 · SE 1.9
Claude (edited photos)	0.5*	n = 10 · SE 0.5

CoralSCOP (edited photos) reads 5.0%, within 4.5 pp of Claude's blind point count (0.5%).

*Based on only 10 reef-habitat photos; this estimate is less certain.

See a more detailed, stand-alone version of this table.

Data & links

All images from Coral Reef Diagnostics. Data are from Coral Reef Diagnostics and NOAA Coral Reef Watch.